Intravenous propranolol had variable effects in 12 patients with PSVT, reducing sustained PSVT in some (from 9 to 5 patients) while potentiating echo zones in others.
Does intravenous propranolol alter the induction and characteristics of A-V nodal reentrant paroxysmal tachycardia in patients with PSVT?
Intravenous propranolol demonstrates variable electrophysiological effects in patients with PSVT, offering potentially beneficial slowing or termination of tachycardia, but also potentially deleterious potentiation of echo zones.
Twelve patients with paroxysmal supraventricular tachycardia (PSVT) were studied before and after administration of 0.1 mg/kg i.v. propranolol. Echo zones for inducing atrioventricular (A-V) nodal reentry were determined using His bundle recording and the atrial extrastimulus technique. After propranolol the echo zone was abolished in two patients, decreased in one, unchanged in five, increased in two. In two patients echo zones appeared only after propranolol. Nine patients had episodes of sustained PSVT prior to propranolol. Following propranolol PSVT persisted in only five. In these five patients propranolol slowed the rate of PSVT. The data were analyzed by plotting A 1 -A 2 and H 1 -H 2 interval curves. On the basis of these curves the patients were separated into those with "dual pathways" and those with "reflection." The effects of propranolol on both conduction patterns are discussed. In summary, the actions of propranolol in PSVT patients were variable. Potentially beneficial effects included slowing of induced PSVT, loss of the ability to sustain PSVT, and decrease or total elimination of echo zones. Potentially deleterious effects included potentiation of the echo phenomenon with either increase or development of echo zones.
Wu et al. (Tue,) conducted a other in paroxysmal supraventricular tachycardia (PSVT) (n=12). Propranolol vs. Baseline (before administration) was evaluated on Echo zones for inducing A-V nodal reentry and sustained PSVT. Intravenous propranolol had variable effects in 12 patients with PSVT, reducing sustained PSVT in some (from 9 to 5 patients) while potentiating echo zones in others.